The invention relates to motor drive systems, in general, and more particularly to cyclic duty motor drive systems.
In cyclic duty motor drives, high and repeated accelerations and decelerations constitute the major portion of the operating cycle. Therefore, the operating efficiency of the system depends to a great extent on the losses during acceleration and decleration only.
The conventional approach to control of a cyclic duty motor drive has been to generate either linear ramps or a combination of linear and flat speed profiles. See for instance "Mechanics and Positioning Control of Feeder Drives" by Larry Enterline and John Davison" in The Magazine of Industrial Motion and Control March 1982, pp. 47-50 and April 1982, pp. 41-44. The aforementioned articles also suggest the use of microprocessing within a digital length controller.
Optimal control of a cyclic duty motor drive system of such performance index as will minimize losses is essential. Optimal control is also desirable taking advantage of modern microprocessor-based controller techniques, in particular, on adjustable speed drives operating on a load moved from one position to another within a specified amount of time, e.g., a motor drive embodying what is known as a "length controller". Typical applications thereof are the feed-to-stop and the flying die, or rotary shear systems. The present invention will be described hereinafter in this particular context.